Method for manufacturing laminated substrate with piezoelectric film

Abstract

[Problem] To provide a method for manufacturing a laminated substrate with a piezoelectric film, the method enabling efficient formation of the piezoelectric film on a target substrate while ensuring quality such as piezoelectric performance. [Solution] A manufacturing mechanism A comprises a box-shaped acrylic box 1. Inside the acrylic box 1, a conveying unit 2, a spray coating unit 3, a drying / cooling unit 4, and a baking unit 5 are provided. The manufacturing mechanism A also comprises a low humidity gas supply unit, and can control the humidity of the internal environment of the acrylic box 1 by supplying dry air into the acrylic box 1. The low humidity gas supply unit can control the humidity of the internal environment of the spray coating unit 3. Furthermore, a firing furnace 50 constituting the firing unit 5 comprises a temperature / humidity control device, and is configured to be capable of controlling the temperature and humidity in the furnace to constant values when firing the substrate inside the firing furnace 50.

Description

Method for manufacturing a laminated substrate with a piezoelectric film

[0001] The present invention relates to a method for manufacturing a laminated substrate with a piezoelectric film.

[0002] In recent years, laminated substrates with piezoelectric films have been widely used in various applications such as ultrasonic sensors and probes for medical echocardiograms.

[0003] In this laminated substrate with a piezoelectric film, the piezoelectric film formed on the substrate has a piezoelectric effect that converts electrical energy and mechanical energy. For example, by applying an alternating voltage, a vibrator can emit ultrasonic waves.

[0004] As one method for manufacturing a laminated substrate with a piezoelectric film, a piezoelectric material solution composed of a composite of a piezoelectric sol-gel solution and piezoelectric powder is spray-coated on the surface of the substrate, and then fired to form a coating film that becomes a piezoelectric film (for example, see Patent Document 1).

[0005] Here, in the method for manufacturing a laminated substrate with a piezoelectric film described in Patent Document 1, the piezoelectric material solution contains powder, and by spray-coating this, a porous coating film is formed after firing, and a piezoelectric film with flexibility and resistance to thermal shock can be formed.

[0006] Further, the manufacturing method of spray-coating such a piezoelectric sol-gel solution has the advantage that it is easier to form a thin film with a thickness of about several μm compared to the manufacturing method of dicing a bulk material to a desired film thickness (bulk method), and variations in film thickness and the like that are affected by dicing are less likely to occur.

[0007] Japanese Patent No. 6829851

[0008] However, in the method for manufacturing a laminated substrate with a piezoelectric film described in Patent Document 1, there is a problem of low yield, such as the quality of the coating film and the piezoelectric performance on the substrate after manufacturing becoming insufficient due to peeling of a part of the formed thin film.

[0009] For example, if a part of the formed piezoelectric film (thin film) peels off, ultrasonic waves cannot be transmitted and received, and the desired function cannot be imparted to the substrate.

[0010] Furthermore, when wiring the piezoelectric film after deposition so that it can be used as a probe, an anisotropic conductive adhesive is used to attach an FPC (Flexible Printed Circuit) to the upper electrode placed above the piezoelectric film. However, the elasticity of the FPC sometimes caused the piezoelectric film to peel off.

[0011] This invention was conceived in view of the above points, and aims to provide a method for manufacturing a piezoelectric film-coated laminated substrate that can efficiently form a piezoelectric film on a target substrate while ensuring quality such as piezoelectric performance.

[0012] To achieve the above objective, the present invention provides a method for manufacturing a piezoelectric laminated substrate, comprising: forming a piezoelectric film on a substrate using a piezoelectric material solution containing a composite of a sol-gel solution and a powder; a coating step of spray-applying the piezoelectric material solution to the substrate under a first atmosphere in order to substantially fill at least one of the recesses on the substrate surface, or recesses on the surface of the coating film that will become the piezoelectric film laminated on the substrate, or gaps in the coating film, or pores in the coating film with the piezoelectric material solution; a heat treatment step of heat-treating the spray-coated substrate under a second atmosphere; and a transport step of transporting the substrate between the coating step and the heat treatment step via a transport unit that transports the substrate under the first atmosphere and the second atmosphere, wherein the relative humidity of the first atmosphere and the second atmosphere is controlled to be below a predetermined value, and the coating step and the heat treatment step are performed multiple times to laminate the coating film onto the substrate.

[0013] In this process, by spray-coating a piezoelectric material solution containing a composite of a sol-gel solution and powder onto the substrate, a porous, flexible, and thermally shock-resistant piezoelectric film can be formed. Furthermore, compared to piezoelectric material solutions that do not contain powder, the film thickness formed in a single treatment is increased, improving the efficiency of film formation.

[0014] Furthermore, the coating process involves applying the piezoelectric material solution to the substrate under a first atmosphere controlled to have a relative humidity below a predetermined value. This reduces the influence of ambient humidity during spray coating, resulting in a coating film that is free from unevenness and cracking and exhibits good piezoelectric performance. Additionally, moisture that would otherwise prevent the piezoelectric material solution from filling at least one of the following—the recesses on the substrate surface, the recesses on the coating film surface that form the piezoelectric film laminated on the substrate, the gaps in the coating film, or the pores in the coating film—is reduced, allowing the piezoelectric material solution to substantially fill the recesses on the substrate surface, etc. Moreover, when the coating film is formed, the occurrence of recesses on the substrate surface, recesses on the coating film surface, gaps in the coating film, or pores in the coating film, which would serve as starting points for peeling, becomes less likely, resulting in a good coating film that is less prone to peeling.

[0015] It should be noted that "substantially satisfying" as used herein does not mean, for example, that all depressions on the substrate surface are filled with the piezoelectric material solution, but rather that the piezoelectric material solution is filled to the extent that peeling of the coating film is suppressed. Furthermore, "substantially satisfying" as used herein means filling depressions, gaps, or pores in the coating film surface formed by the first spray application of the piezoelectric material solution onto the substrate, and filling depressions, gaps, or pores in the coating film surface formed by subsequent spray applications, and also includes filling depressions, gaps, or pores in the coating film surface found in the coating film formed earlier (for example, the coating film formed by the first spray application) during the second and subsequent spray application processes. The same applies to the notation "substantially satisfying" as used below.

[0016] Furthermore, controlling the relative humidity to be below a predetermined value means that the amount of moisture (water vapor) per unit volume in the air is controlled to be below a predetermined value. For example, this includes reducing the amount of moisture in the air by dehumidifying in the same temperature environment, or by lowering the temperature in the same space.

[0017] Furthermore, the heat treatment process involves heat-treating the spray-coated substrate in a second atmosphere where the relative humidity is controlled to be below a predetermined value. This reduces the influence of ambient humidity during heat treatment, enabling the formation of a coating film that is free from unevenness and cracking and exhibits good piezoelectric performance. Additionally, the heat treatment process reduces moisture that would otherwise hinder the filling of recesses on the substrate surface, recesses on the coating film surface that form the piezoelectric film laminated on the substrate, gaps in the coating film, or pores in the coating film with the piezoelectric material solution. This allows the recesses on the substrate surface to be substantially filled with the piezoelectric material solution.

[0018] Furthermore, in the transport process, by transporting the substrate between the coating process and the heat treatment process via a transport unit that transports the substrate under a first atmosphere and a second atmosphere, the substrate with the piezoelectric material solution spray-coated can be moved in a humidity-controlled environment. This also reduces the influence of ambient humidity on the solution before it hardens on the substrate, making it easier to form a good coating film. In addition, during the transport process, moisture that would otherwise prevent the piezoelectric material solution from filling recesses on the substrate surface, recesses on the coating film surface that will become the piezoelectric film laminated on the substrate, gaps in the coating film, or pores in the coating film is reduced, allowing the piezoelectric material solution to substantially fill recesses on the substrate surface.

[0019] Furthermore, by performing the coating and firing processes multiple times and accumulating the coating films that will become piezoelectric films on the substrate, a piezoelectric film of a desired thickness can be provided on the substrate.

[0020] Furthermore, if the heat treatment process includes a firing process for firing the spray-coated substrate, the piezoelectric material solution applied to the substrate or coating can be fired and solidified into a coating film in a second atmosphere, thereby substantially filling any depressions on the substrate surface with the piezoelectric material solution.

[0021] Furthermore, if the heat treatment process includes a drying process for drying the spray-coated substrate, the spray-coated piezoelectric material solution can be made to blend with the substrate or the baked coating film of the underlying layer, thereby forming an even better coating film. Additionally, this process can be carried out under a second atmosphere, allowing the piezoelectric material solution to substantially fill any depressions on the substrate surface.

[0022] Furthermore, if the heat treatment process includes a cooling step to cool the fired substrate before the next coating step, it is possible to suppress the evaporation of the piezoelectric material solution that will become the next coating film due to the heat generated during firing in the coating film formed on the substrate when spray-coating the piezoelectric material solution that will become the next coating film. In addition, it is possible to form a good coating film that is difficult to peel off.

[0023] Furthermore, if the process includes a coating fixing step in which multiple coating films laminated on a substrate are fixed to the substrate using an insulating polymer adhesive, the peeling of the multiple coating films that form the piezoelectric body can be further suppressed. In addition, the adhesive strength of the polymer adhesive adheres the multiple coating films to the substrate or the lower coating film, making peeling less likely even when external forces are applied. Moreover, because the polymer adhesive is insulating, it can block electrical contact between the piezoelectric body film and the FPC (Flexible Printed Circuit) attached during wiring when the piezoelectric body film is used as a probe, and between the FPC and the substrate that serves as the lower electrode.

[0024] Furthermore, if the coating process includes a vibration step in which the substrate is vibrated after spray coating the piezoelectric material solution, the piezoelectric material solution can more easily penetrate into depressions on the substrate surface, depressions on the surface of the coating film that forms the piezoelectric body film laminated on the substrate, gaps in the coating film, or pores in the coating film, making it even easier to fill the depressions on the substrate surface with the piezoelectric material solution. In addition, it becomes possible to form a coating film that is even more resistant to peeling.

[0025] Furthermore, if the coating process includes an inspection step to inspect the substrate or the coating film laminated on the substrate before and after spray-coating the piezoelectric material solution, the surface shape of the coating film can be determined through inspection. For example, if recesses or other imperfections are found and the product does not meet certain standards, the piezoelectric material solution can be spray-coated again to ensure the quality of the coating film.

[0026] Furthermore, if the first and second atmospheres are controlled to have a relative humidity of 40% or less, it becomes possible to sufficiently reduce the influence of ambient humidity and form a coating film that is free from unevenness and cracking and has good piezoelectric properties.

[0027] Furthermore, if the first and second atmospheres are controlled to have a relative humidity of 20% or less, it becomes possible to more effectively reduce the influence of ambient humidity and form a coating film that is free from unevenness and cracking and has good piezoelectric properties.

[0028] Furthermore, if the transport unit consists of at least one of the following: a robotic arm capable of gripping substrates, a belt conveyor, an AGV (Auto Guided Vehicle), or an AMR (Autonomous Mobile Robot), control instructions can be given to the robotic arm, etc., to automate the operation of transporting the substrates.

[0029] Furthermore, the piezoelectric constant d of the piezoelectric film ３３ When the coefficient of capacitance is 50 pC / N or higher, a laminated substrate with a piezoelectric film that has sufficiently good piezoelectric performance can be obtained.

[0030] The method for manufacturing a piezoelectric film-coated laminated substrate according to the present invention is a method that can efficiently form a piezoelectric film on a target substrate while ensuring quality such as piezoelectric performance.

[0031] This is a schematic plan view showing the general structure of a film substrate manufacturing method, which is an example of a method for manufacturing a piezoelectric film-attached laminated substrate according to the present invention. This is a photograph of the film substrate after the 15th firing in Example 1. This is an image showing the results of operational verification of an ultrasonic array sensor manufactured using the film substrate of Example 1. This is a photograph of the film substrate after the 15th firing in Comparative Example 1. This is a photograph of the film substrate after the 11th firing in Comparative Example 2. This is a photograph of the film substrate after the 1st firing in Comparative Example 3. This is a schematic diagram of the structure of a film substrate on which a piezoelectric film is fixed using a polymer adhesive.

[0032] The following describes embodiments of the present invention to facilitate understanding of the present invention.

[0033] This section describes a method for manufacturing a film substrate, which is an example of a method for manufacturing a piezoelectric film-coated substrate according to the present invention. In the following, the piezoelectric film-coated laminate substrate to be manufactured will be referred to as the "film substrate."

[0034] Here, the manufacturing mechanism A used in the method for manufacturing a film substrate has various devices related to the manufacturing of the film substrate arranged inside thereof, and is a mechanism for manufacturing a film substrate by laminating a piezoelectric film on a target substrate.

[0035] As shown in FIG. 1, the manufacturing mechanism A has a box-shaped acrylic box 1. The acrylic box 1 is provided in a predetermined indoor space or the like and is a member constituting the outer shape of the manufacturing mechanism A. The acrylic box 1 has four side surfaces and one top surface and is a partition member that separates the indoor space from the inside of the manufacturing mechanism A.

[0036] Further, the manufacturing mechanism A has a low-humidity gas supply part (not shown), and can supply dry air inside the acrylic box 1 to control the humidity of the internal environment of the acrylic box 1.

[0037] Further, the manufacturing mechanism A has a temperature adjustment mechanism (not shown) and can control the temperature of the internal environment of the acrylic box 1.

[0038] As shown in FIG. 1, inside the acrylic box 1, a transport part 2, a spray coating part 3, a drying and cooling part 4, and a firing part 5 are provided.

[0039] Here, the transport part 2 is a part responsible for transporting the substrate inside the acrylic box 1. The spray coating part 3 is a part for coating a coating film that becomes a piezoelectric film on the substrate.

[0040] The drying and cooling part 4 is a part where the substrate is placed to dry the piezoelectric material solution spray-coated on the substrate before firing. The drying and cooling part 4 is also a part where the fired substrate is placed to cool it before spray-coating again.

[0041] The firing part 5 is a part for firing the piezoelectric material solution spray-coated on the substrate to form a coating film.

[0042] Further, the transfer unit 2 has a robot arm 20 capable of gripping and transferring a substrate. The robot arm 20 can transfer the substrate inside the acrylic box 1 toward the spray coating unit 3, the drying and cooling unit 4, and the firing unit 5, and is responsible for the movement of the substrate during various processing steps.

[0043] In the vicinity of the robot arm 20, a substrate placement unit (not shown) is provided, on which a substrate before the process of manufacturing the film substrate or the film substrate after manufacturing is placed. The robot arm 20 is configured to transfer the substrate before the process supplied to the substrate placement unit and subject it to various processing steps.

[0044] Further, the driving of the robot arm 20 is controlled via a control unit (not shown), and the transfer of the substrate is configured to grip and transfer the substrate according to a preset processing procedure.

[0045] Here, it is not necessarily required for the transfer unit 2 to have the robot arm 20, and it is also possible to adopt other transfer mechanisms. For example, as a mechanism responsible for transfer, it is also possible to use a belt conveyor, an AGV (Automated Guided Vehicle), an AMR (Autonomous Mobile Robot), or other known transfer means used in a factory or the like.

[0046] Furthermore, specific examples of known transport methods are as follows: AGV (Automated Guided Vehicle): An autonomous vehicle that transports parts along a designated route. AMR (Autonomous Mobile Robot): Unlike AGVs, it can calculate its route in real time and move, offering high flexibility. Linear motor conveyor: Uses magnetism to transport parts quickly and accurately. Lift-type transport device: Capable of transporting parts horizontally and vertically. Screw conveyor: Transports powders and granular parts by rotating a screw. Bucket elevator: A continuous transport machine for transporting parts vertically. (Hybrid and special transport methods) Forklift: Capable of transporting parts along with their pallets. Drone transport: Moves lightweight parts through the air (suitable for special environments and wide areas). (Transport methods that assist human power) Cart with casters: A simple manual transport method. Slider platform: Transports parts by sliding them. Roller conveyor: Moves light parts manually or by gravity. (Others) Vacuum suction transport device: Uses vacuum to suction and transport parts. Magnetic lifter: Moves by attracting magnetic materials. Crane system: Transports heavy objects and large parts.

[0047] Furthermore, the spray coating unit 3 has a box-shaped acrylic coating box 30. The acrylic coating box 30 is a smaller box shape than the acrylic box 1 described above, and is a component that further partitions the space inside the acrylic box 1 for spray coating onto the substrate.

[0048] Furthermore, the coating acrylic box 30 can be supplied with dry air from the low-humidity gas supply unit mentioned above, allowing for control of the humidity of the internal environment of the coating acrylic box 30.

[0049] Furthermore, the internal environment of the acrylic box 1 and the internal environment of the coating acrylic box 30 are configured to allow for individual humidity control via a low-humidity gas supply unit.

[0050] Furthermore, the spray coating unit 3 has a temperature control mechanism (not shown) that allows for control of the internal temperature of the coating acrylic box 30.

[0051] Furthermore, the spray application unit 3 includes a holding jig (not shown) and a spray gun for application. The holding jig and the spray gun are located inside the acrylic box 30 for application, with the spray gun attached to the holding jig.

[0052] Furthermore, a slit is formed in a part of the side of the acrylic coating box 30, through which the tip of the robot arm 20 holding the substrate can pass. This allows the tip of the robot arm 20 holding the substrate to move the substrate even inside the acrylic coating box 30.

[0053] In this spray coating section 3, the tip of the robot arm 20, which is gripping the substrate, enters the inside of the coating acrylic box 30, and the coating spray gun applies the piezoelectric material solution to the held substrate.

[0054] Furthermore, the spray gun for coating is controlled via a control unit (not shown) and is configured to spray coating onto the substrate according to a preset processing procedure.

[0055] Furthermore, when applying the piezoelectric material solution to the substrate, a mask member with multiple slits is placed on top of the substrate, and a spray gun for application is configured to apply a fixed amount of solution from above the mask member. The robot arm 20 also holds the mask member together with the substrate.

[0056] In other words, the piezoelectric material solution that has passed through the regions of multiple slits in the mask member is applied to the substrate, or onto a coating film formed on the substrate.

[0057] Furthermore, the spray coating section 3 is equipped with a vibrator to apply vibration to the substrate held by the robot arm 20. By applying vibration to the substrate coated with the piezoelectric material solution, the piezoelectric material solution can be more easily filled into the recesses on the surface of the substrate.

[0058] Furthermore, when a coating film is formed after the substrate has been fired, and a piezoelectric material solution is spray-applied onto the coating film using a spray gun, similarly, vibration can be applied with a vibrator to facilitate the filling of depressions, gaps, and pores on the surface of the coating film with the piezoelectric material solution.

[0059] Furthermore, the spray coating unit 3 is provided with an imaging unit (not shown). This imaging unit acquires an image of the substrate surface or the coating surface before or after spray coating the piezoelectric material solution.

[0060] This imaging unit can acquire images of the substrate surface or coating surface, and the surface shape can be inspected based on the acquired images.

[0061] For example, after spray-coating a piezoelectric material solution, the degree to which the piezoelectric material solution fills depressions and gaps on the surface of a substrate (such as the extent of unfilled depressions) can be observed, and if certain standards are not met, measures such as re-coating the solution can be taken. Furthermore, a CCD camera or similar imaging device can be used to inspect for foreign matter on the surface.

[0062] Furthermore, as shown in Figure 1, the drying and cooling section 4 has a heat-resistant metal base 40. The heat-resistant base 40 is a platform-shaped member larger than the substrate, and is the part on which the substrate after spray coating or the substrate after firing, which has become hot, is placed.

[0063] Furthermore, as shown in Figure 1, the firing section 5 has a firing furnace 50. The firing furnace 50 also has a temperature and humidity control device, which is configured to control the temperature and humidity inside the furnace to constant values ​​when firing substrates inside the furnace 50.

[0064] Next, we will explain the process for manufacturing a film substrate using manufacturing mechanism A. The following description is an example of a method for manufacturing a piezoelectric laminate substrate to which the present invention is applied.

[0065] First, as a piezoelectric material solution to be applied to the substrate, lead zirconate titanate (PZT) sol gel solution and PZT powder were mixed in a certain ratio and stirred in a ball mill for more than 24 hours to obtain the piezoelectric material solution.

[0066] Furthermore, a stainless steel (SUS304) substrate was used as the base substrate for manufacturing the film substrate.

[0067] Here, the piezoelectric material solution does not necessarily have to consist of a lead zirconate titanate (PZT) sol-gel solution and PZT powder; other sol-gel solutions and powdered raw materials can be used.

[0068] For example, as a sol-gel solution, a piezoelectric material having piezoelectric properties due to the anisotropy of its crystals can be used in a state between sol and gel, known as a sol-gel. As the piezoelectric material, for example, lead zirconate titanate (PZT) as described above can be used. Furthermore, lithium niobate and other piezoelectric materials with known piezoelectric properties can be used as raw materials in a sol-gel form.

[0069] Furthermore, as the powder, a piezoelectric material having piezoelectric properties due to the anisotropy of its crystals can be used in powder form. For example, lead zirconate titanate (PZT) as described above can be used. In addition, lithium niobate and other piezoelectric materials with known piezoelectric properties can be used as raw materials in powder form.

[0070] Furthermore, the sol-gel solution and powder that constitute the piezoelectric material solution do not necessarily need to possess piezoelectric properties themselves; it is sufficient if the combined sol-gel solution and powder possess piezoelectric properties.

[0071] Furthermore, it is not necessarily required that a SUS304 substrate be used as the base substrate for manufacturing the film substrate; substrates used in known film substrates can be used. For example, substrates such as SUS304, SUS430, titanium, copper, and aluminum can be used.

[0072] Furthermore, the internal environment of the acrylic box 1 is controlled via a low-humidity gas supply unit to maintain a relative humidity of 40% or less, in order to substantially fill the minute surface recesses on the substrate with a piezoelectric material solution. The internal environment of the acrylic box 1 is also controlled to a temperature of 25°C via a temperature control mechanism.

[0073] Here, the internal environment of the acrylic box 1 can be set to, for example, a relative humidity of 40% or less, or a relative humidity of 20% or less, in order to substantially fill the minute surface recesses on the substrate with the piezoelectric material solution.

[0074] Furthermore, in the transport unit 2, the robot arm 20 grasps the substrate placed in the substrate mounting unit and transports the substrate to the spray coating unit 3.

[0075] Furthermore, the tip of the robot arm 20, which has passed through the slit in the coating acrylic box 30, holds the mask member on top of the substrate, and the robot arm 20 faces the coating spray gun, which is fixed by a holding jig.

[0076] In this process, the internal environment of the coating acrylic box 30 is controlled via a low-humidity gas supply unit to maintain a relative humidity of 40% or less, in order to substantially fill the minute surface recesses on the substrate with the piezoelectric material solution. Furthermore, the internal environment of the coating acrylic box 30 is controlled to a temperature of 25°C via a temperature control mechanism.

[0077] Here, the internal environment of the coating acrylic box 30 can be set to, for example, a relative humidity of 40% or less, or a relative humidity of 20% or less, in order to substantially fill the minute surface recesses on the substrate with the piezoelectric material solution.

[0078] Then, based on a pre-set program control, the power to the coating spray gun is turned ON, and the piezoelectric material solution is sprayed from the coating spray gun. The tip of the robot arm 20 moves the substrate in response to this, so that the solution is uniformly applied to the substrate, adding slits to the mask member.

[0079] Furthermore, once a certain amount of piezoelectric material solution has been sprayed, the power to the coating spray gun is turned OFF, the robot arm 20 removes the mask member, and moves the substrate outside the coating acrylic box 30.

[0080] The robot arm 20 then transports the substrate from the spray coating unit 3 onto the heat-resistant base 40 of the drying and cooling unit 4, and dries the applied piezoelectric material solution on the substrate on the heat-resistant base 40 for about 5 to 10 minutes.

[0081] Furthermore, after drying the substrate in the drying and cooling section 4, the robot arm 20 transports the substrate into the firing furnace 50 of the firing section 5. Inside the firing furnace 50, the substrate is separated from the tip of the robot arm 20 at the position where firing takes place, and the substrate is set in a predetermined position.

[0082] Furthermore, in the firing furnace 50, the substrate is fired at a temperature of 400°C to 650°C for about 3 to 5 minutes. This firing causes the piezoelectric material solution applied by the spray coating section 3 to solidify, forming a coating film on the substrate.

[0083] In this process, in order to substantially fill the minute surface depressions on the substrate with the piezoelectric material solution, the internal environment of the firing furnace 50 is controlled via a temperature and humidity control device so that the relative humidity is 40% or less.

[0084] Here, the internal environment of the firing furnace 50 can be set to, for example, a relative humidity of 40% or less, or a relative humidity of 20% or less, in order to reduce moisture that would prevent the piezoelectric material solution from filling minute surface depressions on the substrate.

[0085] After the firing process in the firing furnace 50, the robot arm 20 grasps the substrate, and the substrate is transported onto the heat-resistant base 40 of the drying and cooling section 4. The substrate, which has become hot due to firing, is placed on the heat-resistant base 40 for about 10 minutes to cool down.

[0086] After the substrate is cooled in the drying and cooling section 4, the robot arm 20 transports the substrate to the spray coating section 3.

[0087] Following this, the piezoelectric material solution is spray-coated onto the coating formed on the substrate, in the same manner as described above. Similarly, the substrate is then dried, fired, and cooled.

[0088] Thus, when spray-coating a piezoelectric material solution onto a coating film (first coating layer) formed on a substrate to form another coating film (second coating layer), the same process described above is followed to substantially fill minute depressions, gaps, or pores on the surface of the first coating layer with the piezoelectric material solution that will become the second coating layer. Furthermore, "substantially filling" here also includes filling depressions, gaps, or pores on the surface of the coating film (e.g., the first coating layer) that were formed earlier, during the second and subsequent spray-coating processes.

[0089] Furthermore, when spray-coating a piezoelectric material solution onto a coating film (first coating layer) formed on a substrate to form another coating film (second coating layer), cooling the substrate before the spray coating process can remove the heat generated during the firing of the first coating layer.

[0090] According to this method, when a piezoelectric material solution is spray-applied onto the first coating layer, the piezoelectric material solution evaporates due to heat, preventing the formation of minute depressions, gaps, pores, etc., on the surface of the resulting coating (second coating layer). As a result, the peeling of the coating layered on the substrate can be prevented.

[0091] In this process, from spray coating to substrate cooling, a coating film approximately 10 μm thick can be formed. Therefore, by performing the spray coating and substrate firing processes multiple times, multiple coating films can be layered on the substrate, and the desired thickness can be achieved for the entire layered coating film.

[0092] Furthermore, after performing spray coating and substrate firing processes multiple times to form a coating of the desired thickness, a corona discharge polarization device is used to apply a voltage (for example, 30 kV per 100 μm) to the coating to perform polarization treatment. This polarization treatment imparts piezoelectricity to the coating.

[0093] By adding electrodes and wiring to a substrate that has undergone this polarization treatment, sensors such as ultrasonic array sensors can be constructed.

[0094] Furthermore, regarding the film substrate manufactured here, the piezoelectric constant (d3) that indicates the piezoelectric performance of the piezoelectric film is used. ３３When measured, the result is 50 pC / N or higher, indicating that a piezoelectric film with good piezoelectric performance can be formed.

[0095] Furthermore, regarding the film substrate described above, in order to prevent the piezoelectric film from peeling off, it is conceivable that the piezoelectric film may be fixed to the substrate using a polymer adhesive.

[0096] In the structure shown in Figure 7, a piezoelectric film (PZT layer) 101 is laminated onto a SUS plate 100 using the method described above, and an upper electrode 102 is provided on top of it. A polymer adhesive 103 is then applied to the piezoelectric film 101 to fix it to the SUS plate 100.

[0097] This polymer adhesive 103 is applied to the area of ​​the piezoelectric film 101 where the upper electrode 102 is not attached, and to the SUS plate 100. This polymer adhesive 103 is composed of an insulating epoxy adhesive.

[0098] In the structure shown in Figure 7, the piezoelectric film 101 is fixed to the SUS plate 100 by the polymer adhesive 103, thereby preventing the piezoelectric film 101 from peeling off from the SUS plate 100.

[0099] Furthermore, the electrode 105 of the FPC 104 is fixed to the upper electrode 102 via an anisotropic conductive adhesive 106.

[0100] Here, by fixing the piezoelectric film 101 with polymer adhesive 103, when an external force is generated that would cause the piezoelectric film 101 to peel off due to the elasticity of the FPC 104, it is possible to prevent the piezoelectric film 101 from peeling off from the SUS plate 100.

[0101] Furthermore, since the polymer adhesive 103 is insulating, it is possible to prevent the electrodes 105 of the FPC 104 from making unintended electrical contact with the piezoelectric film 101 or the SUS plate 100 (lower electrode).

[0102] Here, the polymer adhesive 103 can be appropriately selected as long as it is a component that can be cured to fix the piezoelectric film 101 and has insulating properties.

[0103] Furthermore, the polymer adhesive 103 can be attached not only by application, but also by immersing the SUS plate 100 and the piezoelectric film 101 in the liquid polymer adhesive before it hardens, thereby adhering them to desired locations on the SUS plate 100, etc.

[0104] Furthermore, the polymer adhesive 103 can be attached to the piezoelectric film 101 either after or before the upper electrode 102 is installed.

[0105] Thus, in the method for manufacturing a film substrate to which the present invention is applied, peeling of the piezoelectric film from the substrate can be prevented by using a polymer adhesive.

[0106] In the manufacturing method of a film substrate using the manufacturing mechanism A described above, the humidity is controlled to be low so that the relative humidity is 40% or less in the internal environment of each of the various processes performed in the spray coating section 3, the drying and cooling section 4, and the firing section 5. This makes it possible to substantially fill minute surface recesses on the substrate, as well as minute surface recesses, gaps, or pores in the coating film laminated on the substrate, with the piezoelectric material solution.

[0107] First, by controlling the relative humidity of the internal environment in the spray coating section 3 to 40% or less, the adverse effects of ambient humidity on the paint on the substrate after spray coating and before it hardens through firing can be reduced, thereby preventing unevenness and cracking in the coating film after firing. In addition, it is possible to prevent a decrease in the piezoelectric performance of the piezoelectric film due to the effects of humidity.

[0108] Furthermore, by controlling the relative humidity in the internal environment where the drying and cooling unit 4 is provided, i.e., the internal environment of the acrylic box 1, to 40% or less, the adverse effects of humidity in the environment during the drying of the piezoelectric material solution coating applied to the substrate can be reduced, thereby preventing unevenness and cracking in the coating film after firing. In addition, it is possible to prevent a decrease in the piezoelectric performance of the piezoelectric material film due to the effects of humidity.

[0109] In particular, when drying the substrate in the drying and cooling section 4, when spray-applying paint on top of the coating already formed on the substrate to create a layer of coatings, the paint applied from above adheres more easily to the surface of the lower coating, making it easier to form a strong coating that is less prone to peeling overall.

[0110] Furthermore, by controlling the relative humidity inside the acrylic box 1 to 40% or less, it becomes possible to reduce the adverse effects of ambient humidity on the coating film when the robot arm 20 transports the substrate.

[0111] Furthermore, by controlling the relative humidity of the internal environment in the firing furnace 50 of the firing section 5 to 40% or less, the adverse effects of ambient humidity on the paint on the substrate before firing and on the coating film shortly after firing can be reduced, thereby preventing unevenness and cracking in the coating film after firing. In addition, it is possible to prevent a decrease in the piezoelectric performance of the piezoelectric material film due to the effects of humidity.

[0112] Next, we will explain a modified version of manufacturing mechanism A.

[0113] In the manufacturing mechanism A described above, the firing section 5 had a firing furnace 50, but a hot plate can be used instead of the firing furnace 50.

[0114] In this case, the substrate dried in the cooling and drying section 4 is transported to the hot plate via the robot arm 20, where it is heated and fired. Furthermore, in this modified example, the humidity inside the acrylic box 1 is controlled, allowing for the formation of a good coating film.

[0115] As described above, the method for manufacturing a piezoelectric film-coated laminated substrate to which the present invention is applied is a method that can efficiently form a piezoelectric film on the target substrate while ensuring quality such as piezoelectric performance.

[0116] [Examples] Examples and comparative examples of the present invention will be described below.

[0117] (Example 1) A modified version of the manufacturing mechanism A described above (using a hot plate in the firing section 5) was used to manufacture a film substrate according to the following procedure. A SUS304 substrate measuring 120 mm × 120 mm × 0.05 mm was used. The day before the test, a lead zirconate titanate (PZT) sol gel solution and PZT powder were mixed and stirred in a ball mill machine. The untreated substrate was transported by a robot arm 20, and the piezoelectric material solution was spray-coated onto the substrate in the spray coating section 3. The coated substrate was then dried for 5 to 8 minutes in the cooling and drying section 4. After that, the substrate was transported to a hot plate and fired at 450°C for 3 minutes. After firing, the substrate was cooled in the cooling and drying section 4 for 8 minutes. Thereafter, spray coating, drying, firing, and cooling were repeated, and a total of 15 spray coatings were performed. Furthermore, the relative humidity in the spray coating section 3 (inside the coating acrylic box 30), the drying and cooling section 4, and the firing section 5 (inside the acrylic box 1) was set to 16%. The 15th firing was performed at a temperature of 650°C for 3 minutes. After cooling, the substrate was subjected to polarization treatment using a corona discharge polarization device, and this was designated as Example 1.

[0118] For the film substrate of Example 1, d ３３ Using a meter (manufactured by the Institute of Acoustics, Chinese Academy of Sciences, Model ZJ-3B), the piezoelectric constant (d) of the piezoelectric film was determined. ３３ The following measurements were taken. In addition, electrodes and wiring were provided on the film substrate of Example 1 to construct an ultrasonic array sensor, and its operation was verified.

[0119] Figure 2 is a photograph of the film substrate after the fifth firing in Example 1. As shown in Figure 2, the film substrate S1 of Example 1 has a neatly laminated piezoelectric film and a coating with a good appearance.

[0120] Piezoelectric constant (d) of Example 1 ３３ The ratio was 70 pC / N. Furthermore, the film thickness of the PZT film deposited in Example 1 was 147 μm.

[0121] Figure 3 shows the results of the operational verification of the ultrasonic array sensor manufactured using the membrane substrate of Example 1. Figure 3 is a B-mode image of the string target. In this image, the upper part of the figure is near the body surface, and the lower part is deep inside the body. The further down (deeper) the white dots are visible in the figure, the better the sensor is, and the smaller each white dot appears, the better the sensor is. As shown in Figure 3, small white dots were observed in the lower part of the figure.

[0122] (Example 2) A film substrate was prepared using the same method as in Example 1, except for the conditions described below, and this was designated as Example 2. Spray coating, drying, firing, and cooling were repeated, resulting in a total of 13 spray coatings. In addition, the relative humidity in each space of the spray coating section 3 (inside the coating acrylic box 30), the drying and cooling section 4, and the firing section 5 (inside the acrylic box 1) was kept within the range of 22-35%.

[0123] Piezoelectric constant (d) of Example 2 ３３ The ratio was 59 pC / N. In addition, the film thickness of the PZT film deposited in Example 2 was 97 μm.

[0124] (Example 3) A film substrate was prepared using the same method as in Example 1, except for the conditions described below, and this was designated as Example 3. The relative humidity in the spray coating section 3 (inside the coating acrylic box 30), the drying and cooling section 4, and the firing section 5 (inside the acrylic box 1) was kept within the range of 24-29%.

[0125] Piezoelectric constant (d) of Example 3 ３３ The ratio was 60 pC / N. In addition, the film thickness of the PZT film deposited in Example 3 was 120 μm.

[0126] Next, following the same procedure as in Example 1 above, film substrates were manufactured in the spray coating section 3 (inside the coating acrylic box 30), the drying and cooling section 4, and the firing section 5 (inside the acrylic box 1) without humidity control, using the laboratory environment, and these were used as various comparative examples.

[0127] (Comparative Example 1) In Comparative Example 1, the relative humidity in the laboratory was 58%. In Comparative Example 1, unevenness was observed in the coating film on the substrate after the first spray coating and firing. Furthermore, after the 15th spray coating and firing, cracks occurred in the coating film on substrate S2, as shown in Figure 4.

[0128] (Comparative Example 2) Comparative Example 2 was tested on a different day than Comparative Example 1, and the relative humidity in the laboratory was 66%. In Comparative Example 2, after the first spray coating and firing, rosettes (crystal-like lumps) were observed in the coating film on the substrate. Furthermore, after the eleventh spray coating and firing, cracks occurred in the coating film on substrate S3, as shown in Figure 5. In addition, the piezoelectric constant (d) of the piezoelectric film was measured in areas without cracks. ３３ The measurement of ) showed a value of 30 pC / N.

[0129] (Comparative Example 3) Comparative Example 3 was tested on a different day than Comparative Examples 1 and 2, and the relative humidity in the laboratory was 70%. In Comparative Example 3, as shown in Figure 6, rosettes (crystal-like clumps) were observed in the coating film on the substrate S4 after the first spray coating and firing. Furthermore, large cracks appeared in the coating film after the third spray coating and firing.

[0130] (Comparative Example 4) Comparative Example 4 was tested on a different day than Comparative Examples 1-3, and the relative humidity in the laboratory was within the range of 42-57%. In Comparative Example 4, after the 10th spray application, unevenness in the coating film was observed, visible to the naked eye and through image analysis.

[0131] A. Manufacturing mechanism 1. Acrylic box 2. Conveying unit 20. Robot arm 3. Spray coating unit 30. Acrylic box for coating 4. Drying and cooling unit 40. Heat-resistant base 5. Firing unit 50. Firing furnace

Claims

1. A method for manufacturing a laminated substrate with a piezoelectric film, comprising: forming a piezoelectric film on a substrate using a piezoelectric material solution containing a composite of a sol-gel solution and a powder, the method comprising: a coating step of spray-applying the piezoelectric material solution to the substrate under a first atmosphere in order to substantially fill at least one of the recesses on the substrate surface, recesses on the surface of a coating film that will become the piezoelectric film laminated on the substrate, gaps in the coating film, or pores in the coating film with the piezoelectric material solution; a heat treatment step of heat-treating the spray-coated substrate under a second atmosphere; and a transport step of transporting the substrate between the coating step and the heat treatment step via a transport unit that transports the substrate under the first atmosphere and the second atmosphere, wherein the relative humidity of the first atmosphere and the second atmosphere is controlled to be below a predetermined value, and the coating step and the heat treatment step are performed multiple times to laminate the coating film onto the substrate.

2. The method for manufacturing a piezoelectric film-coated laminated substrate according to claim 1, wherein the heat treatment step includes at least one of the following steps: a firing step for firing the spray-coated substrate, a drying step for drying the spray-coated substrate, or a cooling step for cooling the fired substrate before the next coating step.

3. A method for manufacturing a laminated substrate with a piezoelectric film according to claim 1 or 2, comprising a coating film fixing step of fixing a plurality of coating films laminated on the substrate to the substrate using an insulating polymer adhesive.

4. A method for manufacturing a laminated substrate with a piezoelectric film according to claim 1 or 2, further comprising a vibration step of vibrating the substrate after spray coating the piezoelectric material solution in the coating step.

5. A method for manufacturing a laminated substrate with a piezoelectric film according to claim 1 or 2, further comprising an inspection step of inspecting the substrate or the coating film laminated on the substrate before and after spray coating the piezoelectric material solution in the coating step.

6. The method for manufacturing a laminated substrate with a piezoelectric film according to claim 1 or 2, wherein the first atmosphere and the second atmosphere are controlled to have a relative humidity of 40% or less.

7. The method for manufacturing a piezoelectric film-equipped laminated substrate according to claim 6, wherein the first atmosphere and the second atmosphere are controlled to have a relative humidity of 20% or less.

8. The method for manufacturing a laminated substrate with a piezoelectric film according to claim 1 or 2, wherein the transport unit is at least one of a robot arm capable of gripping a substrate, a belt conveyor, an AGV (Auto Guided Vehicle), or an AMR (Autonomous Mobile Robot).

9. Piezoelectric constant d of the piezoelectric film ３３ A method for manufacturing a laminated substrate with a piezoelectric film according to claim 1 or claim 2, wherein the ratio is 50 pC / N or more.

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